Conventionally, Patent Document 1 discloses a two-stage compression refrigeration cycle device for increasing the pressure of refrigerant (for example, helium gas) in multiple stages by use of a plurality of compression mechanisms connected in series. The refrigeration cycle device disclosed in Patent Document 1 employs a low-pressure side compression mechanism whose discharge capacity is larger than that of a high-pressure side compression mechanism to reduce the loads on the respective compression mechanisms.
In the two-stage compression refrigeration cycle using the low-pressure side compression mechanism whose discharge capacity is larger than that of the high-pressure side compression mechanism, both compression mechanisms are sometimes intended to be simultaneously started up under the state of pressure equalization with the distribution of pressure difference between high and low pressures equalized in the cycle, like upon the initial start-up. In this case, the discharge-side refrigerant pressure of the low-pressure side compression mechanism with the large discharge capacity might often become higher than the discharge-side refrigerant pressure of the high-pressure side compression mechanism, which results in the inversion of pressure.
For this reason, in the refrigeration cycle disclosed in Patent Document 1, when the compression mechanisms are intended to be started up under the pressure equalization, first, the high-pressure side compression mechanism with a small discharge capacity is started, and then the low-pressure side compression is started, so as to suppress the occurrence of the pressure inversion described above.